Is it better to flat preflop to try to keep the fish in the pot? I think otherwise 3betting would be quite standard here, I have a decent hand with blockers, and BTN folds enough to 3bets.
On the flop he can call me with Ax, PPs (99-KK), flushdraws.
On the turn, his betting narrows down his range a lot, with weaker PPs he would probably check behind, flushdraws got there, and cant have many worse Ax. Besides I have poor implied odds with my flushdraw (onecard, oop).
What would you play on turn/river?

would you not consider 2nd barrell on the turn since you have the redraw as well? If you get raised there then you know you are behind and since you are planning to call his turn bet I would rather continue myself and then re-evaluate on the river

Preflop: I would most likely just Call and let the fish come along. We don't really want to 3bet and practically make all the weaker range to fold and better range to continue.

As playedFlop: He is folding to CB 80% of the time, do you think it's in a first place good spot to CB even? He will just continue with better hands and while you 3bet preflop which means his Ax hands has you dominated.

As playedTurn: As long his range is very strong here and most likely towards better Ax/flushes I wouldn't really 2nd barrel. Cause what worse Calls you? Rather keep his weak hands in the play and maybe even let him bluff with some floats. If you Bet then any worse folds and better continues.